Polar dinosaur tracks open new trail to past

Date:

August 10, 2011

Source:

Emory University

Summary:

Paleontologists have discovered a group of more than 20 polar dinosaur tracks on the coast of Victoria, Australia, offering a rare glimpse into animal behavior during the last period of pronounced global warming, about 105 million years ago.

Share:

Total shares:

FULL STORY

Photo of the tracks.

Credit: Anthony Martin

Photo of the tracks.

Credit: Anthony Martin

Paleontologists have discovered a group of more than 20 polar dinosaur tracks on the coast of Victoria, Australia, offering a rare glimpse into animal behavior during the last period of pronounced global warming, about 105 million years ago.

The discovery, reported in the journal Alcheringa, is the largest and best collection of polar dinosaur tracks ever found in the Southern Hemisphere.

"These tracks provide us with a direct indicator of how these dinosaurs were interacting with the polar ecosystems, during an important time in geological history," says Emory paleontologist Anthony Martin, who led the research. Martin is an expert in trace fossils, which include tracks, trails, burrows, cocoons and nests.

The three-toed tracks are preserved on two sandstone blocks from the Early Cretaceous Period. They appear to belong to three different sizes of small theropods -- a group of bipedal, mostly carnivorous dinosaurs whose descendants include modern birds. Photos of the tracks, above and below, by Anthony Martin.

The research team also included Thomas Rich, from the Museum Victoria; Michael Hall and Patricia Vickers-Rich, both from the School of Geosciences at Monash University in Victoria; and Gonzalo Vazquez-Prokopec, an ecologist and expert in spatial analysis from Emory's Department of Environmental Studies.

The tracks were found on the rocky shoreline of remote Milanesia Beach, in Otways National Park. This area, west of Melbourne, is known for energetic surf and rugged coastal cliffs, consisting of layers of sediment accumulated over millions of years. Riddled with fractures and pounded by waves and wind, the cliffs occasionally shed large chunks of rock, such as those containing the dinosaur tracks.

One sandstone block has about 15 tracks, including three consecutive footprints made by the smallest of the theropods, estimated to be the size of a chicken. Martin spotted this first known dinosaur trackway of Victoria last June 14, around noon. He was on the lookout, since he had earlier noticed ripple marks and trace fossils of what looked like insect burrows in piles of fallen rock.

"The ripples and burrows indicate a floodplain, which is the most likely area to find polar dinosaur tracks," Martin explains. The second block containing tracks was spotted about three hours later by Greg Denney, a local volunteer who accompanied Martin and Rich on that day's expedition. That block had similar characteristics to the first one, and included eight tracks. The tracks show what appear to be theropods ranging in size from a chicken to a large crane.

"We believe that the two blocks were from the same rock layer, and the same surface, that the dinosaurs were walking on," Martin says.

The small, medium and large tracks may have been made by three different species, Martin says. "They could also belong to two genders and a juvenile of one species -- a little dinosaur family -- but that's purely speculative," he adds.

The Victoria Coast marks the seam where Australia was once joined to Antarctica. During that era, about 115-105 million years ago, the dinosaurs roamed in prolonged polar darkness. Earth's average temperature was 68 degrees Fahrenheit -- just 10 degrees warmer than today -- and the spring thaws would cause torrential flooding in the river valleys.

The dinosaur tracks were probably made during the summer, Martin says. "The ground would have been frozen in the winter, and in order for the waters to subside so that animals could walk across the floodplain, it would have to be later in the season," he explains.

Lower Cretaceous strata of Victoria have yielded the best-documented assemblage of polar dinosaur bones in the world. Few dinosaur tracks, however, have been found.

In the February 2006, Martin found the first known carnivorous dinosaur track in Victoria, at a coastal site known as Dinosaur Dreaming.

In May 2006, during a hike to another remote site near Milanesia Beach, he discovered the first trace fossil of a dinosaur burrow in Australia. That find came on the heels of Martin's co-discovery of the first known dinosaur burrow and burrowing dinosaur, in Montana. The two discoveries suggest that burrowing behaviors were shared by dinosaurs of different species, in different hemispheres, and spanned millions of years during the Cretaceous Period.

Story Source:

The above post is reprinted from materials provided by Emory University. The original item was written by Carol Clark. Note: Materials may be edited for content and length.

July 28, 2015  Scientists write that sea-level rise (3.4 mm/yr) is faster in the Chesapeake Bay region than any other location on the Atlantic coast of North America, and twice the global average (1.7 mm/yr). They ... read more

July 28, 2015  The light-sensing molecules that tell plants whether to germinate, when to flower and which direction to grow to seek more sunlight were inherited millions of years ago from ... read more

July 27, 2015  The Viking hit-and-run raids on monastic communities such as Lindisfarne and Iona were the most infamous result of burgeoning Scandinavian maritime prowess in the closing years of the Eighth ... read more

July 20, 2015  For the first time, advanced technologies made it possible to read parts of a damaged scroll that is at least 1,500 years old, discovered inside the Holy Ark of the synagogue ... read more

July 23, 2015  New research reveals that some of the earliest civilizations in the Middle East and the Fertile Crescent may have been affected by abrupt climate change. These findings show ... read more

July 23, 2015  Measurements of iron speciation in ancient rocks were used to construct the chemistry of ancient oceans. Analysis suggests that it took less oxygen than previously thought to ... read more

July 22, 2015  Animal populations on islands tend to develop weird traits over time, becoming big or small or losing the ability to fly. One less-studied pattern of evolution on islands is ... read more

June 1, 2015  Experts have identified Britain's oldest sauropod dinosaur from a fossil bone discovered on the Yorkshire coast. The vertebra (backbone) originates from a group of dinosaurs that includes the ... read more

Nov. 5, 2014  Unexpectedly one of the largest diamond mines in Africa, Catoca in Angola, holds 118-million-year-old dinosaur, crocodile and large mammal tracks. The mammal tracks show a raccoon-sized animal, ... read more

July 7, 2014  A trio of paleontologists has discovered a remarkable new tracksite in Alaska's Denali National Park filled with duck-billed dinosaur footprints -- technically referred to as hadrosaurs -- that ... read more

Oct. 28, 2013  Two fossilized footprints found at Dinosaur Cove in Victoria, Australia, were likely made by birds during the Early Cretaceous, making them the oldest known bird tracks in Australia. These tracks are ... read more